As a background art utilizing energy of solar radiation, there is a photovoltaic power generation system, a solar heat system, a solar furnace, a distillation device such as a desalination system, a chemical reactor system, or a sunlight illuminating system, for example.
The energy density of solar radiation is about 1 KW/m2. In operating these energy systems at a high energy density, concentration of solar radiation is performed. As a light convergence element for concentrating solar radiation, there is a Fresnel lens or a parabolic mirror, for example.
When solar radiation is concentrated on a solar energy conversion apparatus using a light convergence system having such a light convergence element, it is generally important to make an incident direction of solar radiation agree with an optical axis of the light convergence system for obtaining a high condensing ratio. Namely, solar radiation is utilized at a high condensing ratio in a solar energy system having a tracking mechanism which rotates the light convergence element in response to the variation of the incident direction of solar radiation, and which makes the solar energy conversion apparatus agree with the focal point of the light convergence element.
In order to operate such a solar energy system for a long period of time, durability against strong wind and so forth is requested. When the height of the light convergence element increases, the bad influence of the wind pressure increases remarkably. Therefore, when the light convergence element extending to a high altitude is utilized, the costs in maintaining the mechanical strength of the light convergence element and the tracking mechanism increase. Accordingly, the utilization of the large-scale light convergence element is limited to a certain extent.
Further, in irradiating a fixed region with solar radiation utilizing a plane mirror, there has been a similar problem in enlarging a tracking mechanism.
As another background art, an energy system that is called a heliostat is known. In general, the heliostat includes a plurality of plane mirrors and a plurality of tracking mechanisms which respectively drive the plurality of plane mirrors. A fixed irradiation region is irradiated with solar radiation reflected and concentrated by the plurality of plane mirrors. The heliostat which concentrates solar radiation at a high condensing ratio includes many high-precision tracking mechanisms. In this case, however, the cost of the tracking mechanisms is high, and the reduction thereof is requested.
As another background art on the heliostat, heliostatic light collector is disclosed in the Japanese Laid-Open Patent Publication No. 60-243444. The heliostatic light collector includes a mirror supporting bar, an expansion and contraction bar, and a sun directing bar. However, there has been the problem that solar radiation cannot be concentrated when the light convergence direction is equal to the direction of the sun.
Further, in the heliostat according to the above-mentioned background arts, when a large-scale plane mirror is used, there has been the bad influence due to the above-mentioned wind pressure or the problem due to the enlargement of the tracking mechanism.
As still another background art which is proposed, from such a the point of view, a sunlight convergence apparatus is disclosed in the Japanese Laid-Open Patent Publication No. 51-27347, which includes many small reflectors which can be rotated around respective specified shafts as the centers, a controlling body, and a common link which connects each small reflector to the controlling body. Each small mirror is rotated with the same angular variation by the movement of the controlling body. When the controlling body is in a specified position, each small reflector is at an angle so as to reflect and concentrate a parallel light beam at a specific incident angle toward a specified light-convergence position. The sunlight convergence apparatus is designed so as to concentrate the reflected light from each small mirror to the light-convergence position by controlling the position of the controlling body, in response to the variation of the incident angle of the parallel incident light beam.
In the sunlight convergence apparatus, however, there has been the problem that the condensing ratio is remarkably deteriorated with the increment of the variation of the incident angle of the incident light. However, such a decrease in the condensing ratio is not referred to in the Laid-Open Patent Publication No. 51-27347, and the teaching for overcoming this is not disclosed.
The present invention is made in view of the above, and an object of the present invention is to solve the above-mentioned problems.
Another object of the present invention is to provide a novel solar radiation reflecting apparatus which realizes a high condensing ratio for a wide range of incident angle of incident light, and which simultaneously drives a plurality of reflectors.
Still another object of the present invention is to provide a novel solar energy system which utilizes solar energy with a high condensing ratio.
Still another object of the present invention is to provide a novel solar energy system, in which solar radiation collecting efficiency is high.
Still another object of the present invention is to provide a novel solar energy system at a low-cost.
Still another object of the present invention is to improve the stability or the durability in the operation of the solar energy system against the external environment such as the wind or the sand and dust.